Geneva drive repeat cycle timer

ABSTRACT

A timer having means to rotate a shaft on which there is a first geneva wheel that engages the geneva pinion for a limited part of each revolution. The pinion is in mesh with a second wheel and moves that second wheel in short intervals of motion spaced by relatively long intervals of no motion. If the wheels are the same diameter, the second wheel will rotate at the same instantaneous speed as the first wheel during the time the first wheel drives the pinion. The wheel and pinion may be arranged to provide an overall stepdown speed ratio of, for example, 10:1 between the first and second wheels but by arranging the second wheel to move at the same speed as the first wheel and by locating the electrical contact to be actuated by the second wheel, the timing of the actuation of the contact can be controlled much more accurately than by actuating the contact directly from the first wheel, provided it is acceptable to actuate the contacts during only certain limited intervals of time.

United States Patent Hunt [54] GENEVA DRIVE REPEAT CYCLE TIMER [72,]Inventor: Charles A. Hunt, 512 Bound Line Road,

Wolcott, Conn. 06716 [73] Assignee: North America Philips Corp. NewYork,

[22] Filed: June 4,1970

[21] Appl.No.: 43,356

Johnson ..235/95 X Ham et a1. ..235/91 Primary Examiner-Leonard H. GerinAttorneyDonald P. Gillette [57] ABSTRACT A timer having means to rotatea shaft on which there is a first geneva wheel that engages the genevapinion for a limited part of each revolution. The pinion is in mesh witha second wheel and moves that second wheel in short intervals of motionspaced by relatively long intervals of no motion. 1f the wheels are thesame diameter, the second wheel will rotate at the same instantaneousspeed as the first wheel during the time the first wheel drives thepinion. The wheel and pinion may be arranged to provide an overallstepdown speed ratio of, for example, 10:1 between the first and secondwheels but by arranging the second wheel to move at the same speed asthe first wheel and by locating the electrical contact to be actuated bythe second wheel, the timing of the actuation of the contact can becontrolled much more accurately than by actuating the contact directlyfrom the first wheel, provided it is acceptable to actuate the contactsduring only certain limited intervals of time.

I 8 Claims, 2 Drawing Figures FATENTEUFEB 1% 3 3 SHEET 1 of 2 FIG./

INVENTOR. CHARLES AQHUNT ATTORNEY MENU-Z0 FEB um 3.638.509

sum 2 or 2 l\ INVENTOR. CHARLES A. HUNT BY I 1 ATTORNEY FIELD OF THEINVENTION This invention relates to a repeat cycle timer usingelectromechanical operating means to control the actuation of electricalcontacts by way of a geneva drive arrangement that transforms thecontinuously applied power of rotation to intermittent rotation at arelatively high instantaneous speed.

BACKGROUND OF THE INVENTION In electromechanical timers it is frequentlydesirable to control the opening and closing of electrical contacts at aprecisely determined instant during each repeated cycle. If the cycle isvery long, it is theoretically possible to use a slow speed motor and,if necessary, additional gear reduction to a cam that makes onerevolution each cycle and to arrange cam followers around the peripheryof the path of movement of the cam so that the followers will beactuated at a precise instant during the cycle. The difficulty of suchan arrangement is that small imperfections in the surface of the cam andin the cam followers or the contacts, or small displacements of theangular locations of any cam follower can effect large change in thetimes at which the contacts controlled by that follower are actuated. Asa result, it is impractical to try to provide precise timing of asuccession of rapidly occuring events during one relatively long cycleof a continuously moving electromechanical timer.

BRIEF DESCRIPTION OF THE INVENTION According to the present inventionthe precision of actuation of the contacts may be increased many fold bydriving the cam by a counter drive so that it rotates a revolution inthe same total time as if it were rotated continuously. The drivemechanism is similar to a counter drive with geneva wheels in the formof counter wheels interconnected by geneva pinions, but it is notnecessary that the wheels have numerals on them as they would if theywere actually used in a counter. For simplicity, these wheels will bereferred to as "counter wheels. The first counter wheel also operates asa drive wheel and is connected to the shaft of a main power unit, suchas a synchronous electric motor. A geneva pinion located on an adjacentparallel shaft is engaged by the counter wheel at selected times,normally once each revolution. Furthermore, the pinion is in rotatingengagement with the wheei during only a limited part of a revolution ofthe wheel. Thus the pinion remains stationary while the wheel rotatesthrough most of the revolution until the wheel suddenly engages thepinion and causes the latter to rotate relatively rapidly for a shorttime. By connecting the pinion to another counter wheel the rapid motionof the pinion may be transmitted to the second wheel to cause it to moverapidly while the pinion is rotating.

For example, the first counter wheel may engage the pinion for one-tenthof a revolution of the wheel, and the pinion may be constantly in meshwith the second counter wheel. If the latter has a step-up ratio equalto the stepdown ratio from the first counter wheel to the pinion, thesecond counter wheel will rotate with the same instantaneous speed asthe first wheel, but for only one-tenth of a revolution each time thefirst counter wheel engages the pinion. By providing electrical contactactuators controlled by a cam connected to the second counter wheel, theelectrical contacts may be caused to open or close or both during theperiods of relatively rapid movement of the cam so that, in effect,given the :1 ratio set forth hereinabove, the precision of acc'u'r acyof opening and closing the electrical contact is increased by a factorof 10: 1.

One of the objects of the present invention is to provide an improvedrepeat cycle timer in which the timing operations take place at veryaccurately predetermined times in the cycle. Further objects will becomeapparent from the following specification together with the drawings.

IDENTIFICATION OF THE DRAWINGS FIG. 1 is a side view of a repeat cycletimer constructed according to the invention;

FIG. 2 is an exploded view from the side showing the components of atimer constructed according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,FIG. 1 illustrates a timer comprising a motor 10 mounted on a framepiece 11. The motor shaft 12 passes through an aperture 13 in the frameand has mounted thereon a counter, wheel 14. A knurled portion 16 of theshaft serves to rigidly fix the wheel 14 so that the wheel will rotateat the same speed as the shaft. A second shaft 17 is mounted betweensecond and third frame pieces, 18 and 19 respectively. This shaft isarranged to be able to rotate freely but is not directly connected tothe first shaft 12, although it is aligned axially therewith. A knurledportion 21 serves to fix a second counter wheel 22 thereto in such amanner that when the wheel 22 rotates, the shaft 17 will also rotate. Ascan be seen in FIG. 1 the two counter wheels 14 and 22 are positionedwith only a very small gap 23 between them, and they are axially alignedwith each other.

A third shaft 24 is fixed between the two frame pieces 11 and 18, and ageneva pinion 26 is rotatably mounted thereon. The entire arrangement issuch that the counter wheel 14, which is driven by the motor 10, willengage the pinion 26 at selected times, normally once each revolution,and only for a limited part of each revolution of the wheel. Duringengagement, the pinion will rotate at the same instantaneous speed asthe wheel. Since the pinion 26 is continuously in engagement with thecounter wheel 22, as will hereinafter be more fully explained, its rapidmotion will be transmitted to the wheel 22 causing it to rotate at thesame speed for only a limited part of a revolution of the wheel 14. Thusthe wheel 22 will be moved in short intervals of motion spaced byrelatively long intervals of no motion.

The specific construction of the above-defined components of theinvention is more clearly illustrated in FIG. 2. Generally, each of thewheels 14 and 22 is of known construction comprising a cylindricalcircumferential surface area 27 which often has numerals from 0 to 9printed thereon, although such numerals are not necessary in thisinstance. Each wheel also comprises a cam surface 28, offset from thesurface 27 shown only on wheel 14, and an integral geared portion 29,shown only on wheel 22. The orientation of these wheels must be suchthat the cam surface 28 of the wheel 14 faces the geared portion 29 ofthe other wheel 22.

The cam surface 28 comprises a recess 31, into which the teeth of thepinion 26 mesh, thereby causing the pinion to rotate as the wheel 14turns. To this end, the pinion is provided with two sets of teeth 32 and34. The two sets have the same root diameter and the same crown diameterbut have different axial lengths. The first set of teeth, of which onlythe teeth 32a and 32b are visible, has the greater axial length,generally as long as the cylindrical portion 33 of the pinion. Thesecond set, of which only the teeth 34a-34c are visible, is only half aslong as the first. It will be seen that a tooth from the first set iscapable of engaging both of the wheels 14 and 22 simultaneously, while atooth from the second set is capable of engaging only the wheel 22, atits geared portion 29.

In operation then, the motor 10 causes the wheel 14 to rotatecontinuously at any desired speed. Two teeth 32a and 32b, for example,of the pinion 26 will be in contact with, and riding along the camsurface 28 until the recess 31 approaches. Tooth 344 will be inengagement with the gears 29 of wheel 22. As the rotation of the wheel14 continues, the recess 31 will move to fit over the tooth 32a rotatingthe pinion 26 to a position wherein the tooth 34b will be in engagementwith the gears 29 of wheel 22 and the teeth 32b and 320 will be in aposition to ridealong the cam surface 28. This rotation of the pinion istransmitted directly to the wheel 22,

since the teeth 34a and 32a engage the geared portion 29 of the wheel22. The arrangement is such that the wheel 22 will make one fullrevolution for every revolutions of the wheel 14;

As described above, the wheel 22 is fixed to the shaft 17. Therefore,when the wheel moves, it rotates the shaft also. Mounted behind theframe piece 18, relative to the wheel, and on the shaft 17 is a pair ofdiscs 36 and 37. The edges 38 and 39, respectively, comprise nonuniformcam surfaces, and a pair of cam followers 41 and 42 with theirrespective contact points 43 and 44 are arranged to ride along andfollow the contours of the cams. It should be noted that there may bemore than one pair of discs and more than one pair of cam followers. Thediscs 36 and 37 are releasably fixed to the shaft 17 so that they may beadjusted as desired. Upon proper adjustment, they may be fixed so thatthey rotate when the shaft rotates. The contours in the edges 38 and 39,such as jogs 46 and 47, respectively, have the effect of eitherseparating contact points 43 and 44 or closing them, as desired. Thejogs are preferably sharp drops so that the opening or closing of thecontact points will be fast and efficient and, because the wheel 22 andthe shaft 17 rotate at the same instantaneous angular velocity as thewheel 14 during those intermittent periods of motion of the wheel 22,the exact timing of actuation of the cam followers 41 and 42 may be veryaccurately controlled. This timing of actuation may even be indicated bysetting the edges 38 and 39 to predetermined angular positions indicatedby the numerals on the surfaces of the wheels 14 and 22.

What is claimed is:

l. A timer comprising:

a first shaft;

a motor to rotate said shaft;

a first counter wheel on said shaft;

a geneva pinion to be selectively engaged by said first 0 prises:

a first set of teeth;

a second set of teeth, said second set being arranged to engage only oneof said first and second counter wheels.

3. The timer of claim 1 wherein said first and second counter wheels areof the same diameter so that said second counter wheel will rotate atthe same instantaneous speed as said first counter wheel during the timesaid first wheel drives said pinion.

4. The timer of claim 1 wherein said first and second counter wheels areaxially aligned and juxtaposed with each other, said pinion beingarranged therebetween and in engagement therewith.

5. The timer of claim 1 comprising in addition: a second shaft, saidsecond counter wheel being mounted thereon.

6. The timer of claim 5 in which said rotatable cam surface is fixed tosaid second shaft, to be turned thereby when said second counter wheelis driven by said geneva pinion.

7. The timerof claim 1 comprising in addition: at least one electricalcontact to be actuated by said second counter wheel.

8. The timer of claim 7 in which said electrical contact is actuated bya rotatable cam surface.

1. A timer comprising: a first shaft; a motor to rotate said shaft; a first counter wheel on said shaft; a geneva pinion to be selectively engaged by said first counter wheel; a second counter wheel to mesh with said geneva pinion to be moved thereby in defined intervals, said first counter wheel comprising a cam surface to engage the teeth of said geneva pinion, said cam surface comprising a recess to fit over one of said teeth once each revolution of said first counter wheel, thereby to drive saiD geneva pinion in short intervals of motion.
 2. The timer of claim 1 wherein said geneva pinion comprises: a first set of teeth; a second set of teeth, said second set being arranged to engage only one of said first and second counter wheels.
 3. The timer of claim 1 wherein said first and second counter wheels are of the same diameter so that said second counter wheel will rotate at the same instantaneous speed as said first counter wheel during the time said first wheel drives said pinion.
 4. The timer of claim 1 wherein said first and second counter wheels are axially aligned and juxtaposed with each other, said pinion being arranged therebetween and in engagement therewith.
 5. The timer of claim 1 comprising in addition: a second shaft, said second counter wheel being mounted thereon.
 6. The timer of claim 5 in which said rotatable cam surface is fixed to said second shaft, to be turned thereby when said second counter wheel is driven by said geneva pinion.
 7. The timer of claim 1 comprising in addition: at least one electrical contact to be actuated by said second counter wheel.
 8. The timer of claim 7 in which said electrical contact is actuated by a rotatable cam surface. 